Torque compensating apparatus for tightening threaded fastening elements



RICE ETAL 2,835,365 ToRQuE COMPENSATING APPARATUS FOR TIGHTENING 4 Sheets-Sheet l H. T. M.

THREADED FASTENING ELEMENTS @sa Nu May 20, 1958 Filed oet. 2o,v 1952 s) IN V EN TORS.

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May 20, 1958 H. T. M.. RICE ETAL 2,835,365

ToRQuE COMPENSATING APPARATUS FOR TIGHTENING THREADED FASTENING ELEMENTS Filed Oct. 20, 1952 4 Sheets-Sheet 2 v o Q93 6% ewey M. .AQ/ce, 99 RoeseZJrEA/EA/s IN VEN TORS.

May 20, 1958 H. T. M. RICE x-:TAL 2,835,365

ToRQuE COMPENSATING APPARATUS FOR TIGHTENING THREADED FASTENING ELEMENTS 4 Sheets-Sheet 3 Filed Oct. 20, 1952 A q i R M @WA V r W y A@ A @L ,AHM @A A n, y .A $4 www .Mw 7 a. A In y, A H@ W, .WN W J\V U/ W W W .STEVE/vs, INVENToRs.

44770 HEY.

May 20, 1958 H. T. M. RICE ETAL v 2,835,355 ToRQuE COMPENSATING APPARATUS FOR TIGHTENING THREADED FASTENING ELEMENTS 4 Sheets-Sheet 4 Filed Oct. 20, 1952 H/VQ), Z/Mn B/ RQBERT I.J .STEVEN IN V EN TOR BY MTZQNEY.

TORQUE COMPENSATING APPARATUS FR TIGHTENING THREA DED FASTENING ELE- t MENTS Henry T. M. Rice, San Gabriel, and Robert T. Stevens, Altadena, Calif., assignors, by decree of distribution, to Adele M. Stevens, executrix of the estate of Dillon Stevens, deceased t Application October 20, 1952, Serial No. 315,792

21 Claims. '(Cl. 192-56) 'l` he present invention relates to torque transmitting ap paratus, and more particularly to apparatus -fortightening threaded fastening elements to predetermined torque values.

Some forms of apparatus for tightening threaded fastening elements employ motors to drive the threaded fastening elements through a torque responsive clutch, which releases when a predeterminedtorque is transmitted therethrough. The clutch members may be held in engagement by a suitable holding device, as, for example, a device utilizing a spring, a magnet, or fluid under pressure to supplytthe requisite holding force.

A great variation is found in the torque at which the same clutch releases when operating upon different threaded fastening elements. A free running threaded fastening element encountering very little resistance dure ing its rotation, and coming to a sudden stop against the work, may -be tightened to a certain torque value when the clutch releases. With the same force holding the clutch engaged, a threaded fastening element that encounters slowly increasing torque resistance during its rotation is tightened to a much lesser torque value when the clutch releases. The difference is due to the inertia forces that come into play in both instances. When a fastening element comes to a sudden stop, relatively high inertia forces are present, adding to the holding force on the clutch and producing a relatively high torque on the fastening elements at which clutch release occurs. When the fastening element slowly, or gradually, encounters torque resistance, the inertia forces are much lower, and so is the torque to which the element is tightened when clutch release occurs.

Because of the presence of the inertia forces, the same tool will tighten different fastening elements different degrees, despite the fact that the tool has been preset to hold its clutch engaged with the same holding force.

Accordingly, an object of the present invention is to provide a torque responsive apparatus which minimizes the effect of inertia forces, and tightens the threaded fastening elements to substantially the same desired predetermined torjque despite variations in the resistance encountered by the elements during their rotation.

Another object of the invention is to provide torque responsive Vapparatus embodying a clutch that automatically adjusts itself to disengage more readily when a threaded fastener is relatively free runningand, therefore, subject Vto greater inertia forces, and to maintain the drive more j 2,335,365 Patented May 20, 1958 ICC insuring tightening of the fastening elements to essentially the same extent when it stops suddenly against the work as when it is brought to rest gradually against the work.

Yet another object of the invention is to provide apparatus embodying a 'clutch releasable in response to torque transmitted therethrough, in which the clutch releases at a lower torque value when rapid release occurs than when slow release occurs, so that the threaded fastening elements are `tightened to exactly the same total torque in both instances. This is due to the fact that rapid release is associated with high inertia forces and slow re` lease with low inertia forces. The greater tightening effect of the high inertia forces when added to the lower torque of the clutch when rapid release occurs substantially equals the smaller tightening effect of the lower inertia forces when added to the higher torque of the clutch whe slow release occurs.

This invention possesses many other advantages, and has other objects which may be made more clearly `ap` parent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that (such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section through an apparatus embodying the invention, with all of the parts engaged and in position for rotating a threaded fastening element;

Fig. 2 is a fragmentary section similar to Fig. l, illustrating the primary clutch partially released;

Fig. 3 is a view similar to Fig. 2, illustrating the primary clutch completely released;

Fig, 4 is a diagrammatic view, illustrating the driving and driven clutch teeth of the primary clutch in one engaged position; l

Fig. 5 is a view similar to Fig. 4, disclosing the teeth in another engaged position;

Fig. 6 is a longitudinal View of a torque responsive clutch of a modified form; j

Fig. 7 is a view similar to Fig. 6, illustrating the clutch partially disengaged; j

Fig. 8 is a longitudinal section through still another form of the invention, with the primary clutch` fully eneased;

Fig. 9 is a View similar to Fig. 8, showing the primary clutch partially engaged;

Fig. 10 is an enlarged section of a portion of the primary clutch device on an enlarged scale; j

Fig. l1 is a View, similar to Fig. 4, of a modified form of meshing clutchrteeth in fully engaged position;

Fig. 12 is a View similar to Fig. 11, illustrating the clutch teeth partially disengaged.

In its general aspects, the invention contemplates a torque releasable clutch possessing axial teeth of cam form, in order that the torque being transmitted between the teeth tends to eifect their full disengagement. The teeth are held in engagement with one another by a suitable holding means which may exert a constant holding force thereon. Accordingly, when the torque transmitted through the driving and driven cam type of clutch teeth exceeds a value corresponding to the force of the device tending to hold the teeth engaged, release between the driving and driven clutch teeth occurs. t t

When the device is being employed to tighten a free running threaded fastening element, the clutch releases at a torque corresponding to the holding force of `the particular device that tends to maintain the clutch teeth in engagement. However, in the event the threaded fastening element comes to a sudden stop,the torque at which aestseev it is tightened will not only be the torque corresponding to the holding force tending to maintain the clutch teeth in engagement, but also that due to the inertia forces accompanying the sudden deceleration of the fastening element and the axial acceleration of the clutch members. In order to avoid such effect, the driving or driven clutch members are enabled to yield with respect to one another without disengaging the clutch, such yieldability allowing partial rotation of the driving clutch member with respect to the driven clutch member, and thereby absorbing or compensating for the sudden arresting or stopping of the threaded fastening element, and of vthe axial acceleration of the driven clutch member that is connected thereto. The extent of yieldability lis sufficient to enable the effort tending to accelerate the moving clutch parts to be expended. As a result, the threaded fastening element is subjected to lesser inertia forces than would have been provided had the factor of yieldability of the clutch parts been absent. Of course, if the threaded fastening element gradually encounters resistance, then the inertia forces imposed thereon is less, and the extent of yieldability of the clutch parts is correspondingly less.

Because of the yieldability imparted into the system to compensate for the inertia forces, the torque to which the threaded fastening element has actually been tightened, when the clutch becomes fully disengaged, is the same if the threaded fastening element stops against the work suddenly, or is gradually brought to rest against the work.

The form of invention illustrated in the drawings is of a torque releasable device designed to tighten a threaded fastening element to the predetermined torque value to which the apparatus may have been set. The specific device disclosed is illustrated in the application of Henry T. M. Rice and Robert T. Stevens, Serial No. 286,252, filed May 6, 1952, for Air and Magnetic Releasable Torque Transmitting Apparatus.

The invention, however, is applicable to other specific forms of releasable torque devices.

As shown in the drawings, the apparatus is designed primarily for simultaneously rotating and tightening a threaded fastening element (not shown) to a predetermined torque value. If the threaded fastening element is a nut, it would be receivable within the non-circular socket portion of a head 11 mounted upon the ultimate driven spindle 12 of the device, and secured for rotation therewith by a transversely extending pin 13 which is prevented from shifting from its assembled position by a suitable retaining sleeve 14 slidable on the spindle 12 and the socket head 11. This retaining sleeve is held in position adjacent the transverse pin 13 by a suitable helical compression spring 15 bearing against the sleeve 14 and against the forward housing extension 16 of the releasable torque transmitting device.

The spindle 12 is rotated by imparting suitable rotation to a drive gear 17, this rotation being transmitted to the spindle through a primary clutch 1S and a secondary clutch 19. The drive gear 17 meshes with a pinion 20 suitably connected to a prime mover, such as an electric or air driven motor (not shown). The drive gear 17 is suitably secured on the driving member 21 of the primary clutch 18, which is rotatable in suitable spaced bearings 22 carried in the frame or housing of the apparatus. This frame includes rearward and intermediate walls 23,

24 in which the sup-porting bearings .22 are contained., and also a forward end plate or wall 25 connected to the rear member 23 by an encompassing sleeve or side wall 26, suitably secured to both the forward and `rear walls.

The forward portion of the driving clutch member 21 is provided with axially extending clutch teeth 27 having inclined or cam type driving faces 28 or 28a, which may assume several forms, such as illustrated in Figs. 4 and 5 and also in Figs. 11 and l2, as explained hereafter. These driving clutch teeth 28 engage companion inclined faces 4 29 or 29a on driven clutch teeth 30 provided on the driven member 31 of the primary clutch 18. The rotation of the driven member 31 is imparted to the driving member 32 of the secondary clutch 19 through a slidable spline connection. As illustrated, this spline connection includes opposed longitudinal grooves 33, pro'vided'within the driven member and driving member of the secondary clutch, which receives one or a plurality of ball elements 34 therewithin. These elements, in effect, function as rollable keys, serving to transmit the rotation of the driven member 31 to the secondary driving member 32 while allowing the driven member 31 to shift axially along the driving member. The balls 34 are prevented from dropping out of the longitudinal grooves 33 by suitable snap rings 35 disposed within grooves 36 at the rear end portion of the secondary clutch driving member 32, and also in the forward 4end portion of the primary clutch driven member 31.

The secondary clutch driving member 32 is rotatably mounted within the rear portion of the forward housing extension 16, which is carried in the forward end wall 25 of the main housing of the apparatus, through the agency of the ball bearings 37 serving to transmit radial loads between the secondary driving member 32 and housing extension, as well as to resist axial displacement of the secondary driving member. Disposed just rearwardly of the bearing 37 is an elastic bumper engageable by the forward end of the primary clutch driven member 31. This elastic bumper includes an annular member 3S adapted to engage the ball bearing assembly 37, the member, in turn, being engaged by a rubber orrubberlike ring 39 which has another annular member 40 engaging it. When the driven member 31 of the primary clutch is shifted forwardly to disengage it from the driving member 21 of the primary clutch, its forward motion is limited by engagement with the cushioning device 38-4t1, which also absorbs any shock incident to the bringing of the driven member to rest, so far as its longitudinal movement is concerned.

The driving member 32 of the secondary clutch 19 is provided with a plurality, such as a pair, of diametrically opposed clutch teeth or lugs 41 engageable with a transverse pin 42 extending through a transverse and elongate slot 43 formed through the rearward portion of the spindle or driven member 12 of the secondary clutch. This pin may be of square or rectangular crosssection, and will transmit the rotation of the driving member 32 of the secondary clutch to the spindle 12. The pin 42may be shifted axially away from the driving clutch teeth 41, to disengage the secondary clutch, by axially shifting a sleeve 44 encompassing the spindle 12 through which the pin extends. The pin extends through diametrically opposed square holes 45 in the sleeve 44 in a relatively snug fashion, the sleeve preventing tilting or cocking of the transverse pin 42 in the slot 43. The rear portion of the spindle 12 is piloted within the forward portion of the driving member 32 of the secondary clutch, the spindle 12 projecting outwardly through a boss or bearing support 46 provided on the housing extension 16, which functions as a rotatable bearing for the spindle.

As disclosed in Figs. 1 to 3, inclusive, the rotation of the driving member 21 of the primary clutch is transmitted to the driven member 31 through the coengaging cam type of clutch teeth 27, 30. The torque being transmitted between these teeth tends to shift the driven member 31 axially out of engagement with the driving member 21, because of the slope of the teeth faces. The Idriven clutch teeth 30 are held in engagement with the driving teeth 27 against the disengaging force associated with the transmitted torque by an air, or similar gas, pressure dilferential device. Thus, a plate 47 is secured against axial movement with respect to the driven member 31 of the primary clutch by bearing against a shoulder 48 on the driven member, being retained in this position by a suitable split snap ring 49 disposed in a groove 50 in the driven member.`

A valve stem 51 is attached. to this plate, the stem extending through the hub 52 of the latter. Movement of the stem 51 with respect to the plate in one direction is prevented by a pair of split sleeve elements 53 disposed in a circumferential groove 54 in the valve stern and encompassed by the hub portion 52 of the plate. A ange 55 of the split or segmental sleeve engages the rearward face of the plate, the forward portion ofthe plate hub engaging a very high rate helical compression spring 56 whose other end bears against a retaining split snap ring 57 disposed within a groove 58 in the end portion of the valve stem S1.

'I'he valve stern 51 extends through a forward end closure member 58 forming part of the valve body portion 21a of the driving member 21. This end closure 58 is secured to the driving member by engaging ashoulder 59 on the driving member, being retained thereagainst by a split snap retainer ring 60 disposed in a groove 61 in the driving member. The rearward end of the stem is secured to, or is integral with, a valve head 61 adapted to iit within a cylindrical seat 62 formed in the driving member valve body. When disposed fully within this seat 62, the rearward face 63 of the head engages a stop member 64 tting within and firmly secured to the driv ing member 21 of the primary clutch 18. l

The force tending to hold the clutch teeth 3l) of the driven member 31 fully engaged and meshed with the clutch teeth 27 of the driving member 21 is provided by causing air under pressure to act on the forward face 65 of the valve head 61, to lurge it against the stop mem'- ber 64 and retain it within its cylindrical seat 62. Air from a suitable source (not shown), and under pressure, flows through an inlet line 66 into a stationary swivel tube 67 carried in the rearward end support 23. The forward portion of this tube is rotatable in the central passage 68 of the stop member 64 secured within the driving member of the primary clutch. This latter passage communicates with a radial port 69 having a continuation thereof extending through the driving member 2l of the primary clutch and into a longitudinally extending passage 70 through the drive gear 17. This passage cornmunicates with a longitudinal passage 71 extending in a forward direction through the driving clutch member 21, and on into the chamber 72 of the valve body portion of the driving clutch member disposed rearwardly of the valve body closure member 58.

A Thus, air under pressure is delivered into the chamber 72, which has a relatively small volume. end of the chamber 72 is defined by the valve body'closure plate 58, leakage in a forward direction from the chamber being precluded by a peripheral seal 73 onthe closure member engaging the inner wall of the valve body 21a and also by a rod packing 74 disposed on the closure r member and slidably and sealingly engaging the valve stem 51. Leakage of air from the chamber in a rear- -Ward direction is prevented whenever the valve head `61 is disposed within the cylindrical seat 62. The head carries a peripheral sealing member 75 which is adapted to engage the cylindrical seat 62.

As illustrated in Figs. l, Z and 3, the extent of insertion of the seal ring 75 within the cylindrical seat 62 is of comparatively little extent, being, for example, about l@ of an inch, in order that only a slight forward movement of the valve head 61 effects disengagementof the seal ring from the seat, and allows the air in the chamber 72 and acting on the forward face 65 of the head to pass to its rearward face 63, thus equalizing the pressure on both sides of the head. Such equalizing effectively nullies the force of the air pressure tending to hold the valve head 61 within its cylindrical seat 62 and in contact with the stop member 64, this force also being exerted on the driven member 31 through the spring 56, and tending to The forward hold its teeth 30 engaged with the driving member clutch teeth 27. l l 1 When the valve head 61 i.; shifted forwardly from its seat 62 by the driven member 31, the air pressure not only equalizes on both sides of the head, but it can also exhaust from the valve body chamber 72 through an outlet or exhaust passage 76 which preferably has an orifice '77 threaded therein possessing a comparatively small passage area, to decrease the rate at which the air under pressure can exit from the valve chamber. Accordingly, when the valve head 61 has been shifted forwardly out of engagement from the cylindrical seat 62, very little air is lost from the chamber 72, despite the fact that is still being supplied with air under pressure from the inlet line 66, in view of the restriction to flow offered by the orifice 77.

rlhe air under pressure acts upon the forward face 65 of the valve head 61 and tends to hold it engaged within its seat 62, thereby tending to hold the driven clutch teeth 3l] in fully meshing engagement with the driving clutch teeth 27. When the torque being transmitted is sufhcient to overcome the holding force of the air under pressure within` the valve body 21a, the cam teeth 27, 30 shift the driven member 31 in a forward direction to disengage the valve head 61 from the seat 62. Since it takes only a slight movement of the valve head to effectively remove substantially all of the holding force of the air pressure upon it, full disengagement between the teeth 27, 30 occurs under comparatively no-load conditions, the driven member 31 being shifted longitudinally along the driving member 32 of the `secondary clutch with substantially no load being imposed upon the clutch teeth as they disengage. The driven member 31 is moved forwardly, its forward motion being resisted and arrested by the bumper device 38--40.

The driven clutch member 31 is retained in the above disengaged position by a latch arrangement. The driving member 32 of the secondary clutch 19 has a plurality of radial holes 78 therein containing ball detent members 79, engaged by a tapered rearward cam faceSO on a latch sleeve 81, which is slidable within the driving member 32 of the secondary clutch, and also along a tubular member 82 piloted within the spindle 12 and secured to the secondary clutch pin 42 which passes therethrough. A spring 83 constantly urges the latch sleeve 81 in a rearward direction, causing its cam face to tend to shift the latch balls 79 in a radial outward direction. However, such shifting cannot occun when the driven clutch member 31 is fully engaged with the driving clutch member 21, since the balls 79 then engage the inner cylindrical surface 84 of the driven member 31. When the driven member is shifted in a forward direction to clutch disengaged position, an enlarged bore 85 of the driven member is then placed opposite the balls 79, allowing the latter to be shifted radially outward by the tapered face 80 of the latch sleeve, coming to rest upon a tapered shoulder 86 in thedn'ven member (Fig. 3). When the balls 79 are shifted radially outward, the latch sleeve 81 slides therealong, to place the cylindrical periphery 87 of the sleeve opposite the balls. Accordingly,

the driven member cannot be shifted in a rearward direction to shift the balls radially inward, in view of their engagement with the cylindrical periphery 87 of the latch sleeve. The driven member cannot be reengaged with i the driving member 21 until permitted to do so by the removal of the latch balls 79 from their holding position.

In order to release the latch balls 79, it is necessary to shift the secondary clutch pin 42 out of engagement from the driving lugs or teeth 41 of the secondary clutch 19. This action occurs as a result of shifting the sleeve 44 on the spindle 12, and through whichl the pin 42 extends, in a forward direction along the spindle. When moved in the forward direction, not only is the clutch pin 42 disengaged from the lugs 41, but the sleeve or tube 82 piloted within the forward portion of the spindle is also moved in a forward direction. This action causes engagement of a snap ring 88 at the rearward portion of the sleeve 82 with an internal ange 89 on the latch sleeve, shifting the latter in a forward direction against the force of the latch spring 83, so that the cylindrical periphery 87 of the latch sleeve is removed from behind the latch balls 79. When such removal occurs, the tapered shoul der 86 on the driven member is then effective to shift the latch balls 79, radially inward out of engagement from the shoulder, allowing the driven clutch member 31 to move back into full engagement with the driving clutch member 21, disposing the inner cylindrical surface 84 of the driven member again alongside the latch balls.

The return or resetting engagement of the driven memn ber 31 with the driving member 21 occurs under the influence of a light spring 90, which engages a suitable seat 91 at the rearward portion of the driving member 32 of the secondary clutch, and also bears against the driven plate 47 secured to the driven member. This spring not only reengages the driving and driven clutch teeth 27, 30 with one another, but it also reshifts the valve head 61 back into engagement with its cylindrical seat 62.

The shifting sleeve-82 is moved to secondary clutch disengaging position against the force exerted by a reengaging spring 92, which has one end bearing against the spindle 12, and the other end bearing against the pin 42. This spring constantly urges the secondary clutch pin 42 into engagement with the driving lugs 41. However, the secondary clutch 19 can be shifted into a disengaged position, and maintained in this position, by a shift rod or pin 93 engaging a forward flange 94 on the shift sleeve. This pin may be suitably held in a forward position by a detent mechanism (not shown).

In the operation of the apparatus, the parts occupy the position illustrated in Fig. l, in which the primary and secondary clutches 18, 19 are both engaged, the valve head 61 engaging the stop member 64, with its seal ring 75 disposed within the cylindrical seat 62. Air under the desired pressure is allowed to flow through the inlet line 66 and passages 68-71 into the valve chamber 72, this air acting upon the forward face 65 of the valve head and tending to hold the latter and the driven member 31 in the rearward direction, to secure the primary clutch ii in driving position.

The socket head 11 may then be applied to a nut (not shown) and 'the drive pinion 20 and gear 17 rotated, to rotate the driving member 21 of the primary clutch. Such rearwardmotion is transmitted through the clutch teeth 27, 30 tothe driven member, and from the driven member through the spline 33, 34 to the driving member 32 `of-'the secondary clutch, from where it passes through the transverse pin 42 to the spindle 12 and the socket head V11. As the threaded fastening element, such as the nut (not shown), istightened, the torque transmitted increases, this torque acting through the inclined coengaging clutch teeth 27, l3? and tending to shift the driven clutch member 31 in a forward direction out of engagement from the driving clutch member 21. This action is resisted by the holding force of the air pressure upon the valve head 61. To some extent, the holding force is also being provided by the clutch reengaging spring 90, which, however, is preferably made comparatively light, so that its force is of minor significance.

When the predetermined force or torque is transmitted corresponding to the holding force of the air under pressure, the driven member 31 is shifted in a forward direction, such shifting action being transmitted to the valve head 61 through the high rate compression spring 56. The initial shifting motion of the valve head 61 moves it away from the stop 64 and disposes it out of the cylindrical seat 62. As soon as disengagement from the cylindrical seat occurs, the air on the forward side of the head 61 passes to the rearward side, equalizing the pres- 8 sure on the head and reducing the holding force due to the air pressure to substantially zero. Accordingly, the torque transmitted can shift the driven member 31 in the forward direction to fully disengaged position under substantially no-load conditions.

As soon as the shoulder 86 of the driven member 31 comes opposite the latch balls 79, the spring 83 urges the latch sleeve 31 in a rearward direction, to force the balls outwardly upon the shoulder 86, and thereby hold the driven member 31 in disengaged position With respect to the driving member 21 (Fig. 3). The drive to the spindle 12 and socket head 11 is thereby disrupted. The secondary clutch 19, however, remains in engagement.

When it is desired to reset the primary clutch 18, this action can occur as a result of disengaging the secondary clutch 19. Such disengagement occurs by shifting the secondary clutch contro-l rod 93 to the right, as seen in Fig. 1, this rod engaging the sleeve iiange 94 and moving the sleeve 44 and the clutch pin 42 out of engagement from the driving lugs 41. As stated above, the -rod 93 may be retained in a secondary clutch releasing position by a. suitable detent device (not shown). Such `forward shifting of the sleeve 44- and of the transverse pin 42 carries the tubular element $2 in the forward direction, the snapring 8S engaging the latch sleeve 81 and shifting it forwardly, out of retaining position behind the balls 79, whereupon" the primary clutch reengaging spring becomes effective to shift the driven member 31 back into full engagement with the driving member 21, inclined shoulder 86 on the driven member retraeting the latch balls 79 to their initial position. The spring 911i, of course, also reshifts the valve head 61 into engagement with its seat 62, the air trapped behind the valve head escaping through the orifice 77.

The secondary clutch 19 remains disengaged. Accordingly, despite any rotation that might be imparted to the driving clutch member 32, such rotation is not supplied to the spindle 12 and socket head 11. The motion will only be transmitted to those parts upon shifting of the rod 93 in the opposite direction, or to the left. When this is done, the rod'no longer bears against the sleeve ange, 94, allowing the spring 92 to shift the transverse yclutch pin 42 rearwardly until it engages the lugs or teeth 41 of the secondary clutch driving member 32. The partsare then operable to rotate the socket head 11 and tighten another threaded fastening element to the predetermined torque at which the device may be set (Fig. l).

The torque at which the primary clutch 18 is disengaged depends upon the air pressure in the valve `body 21a acting upon the forward face 65 of the valve head, and also upon the slope of the cam teeth 27, 30 at their point of engagement. The steeper the tangent at the point of engagement, the greater is the torque that must be transmitted through the clutch teeth for the same holding force, in order to effect disengagement of the primary clutch. v Such disengagement occurs under substantially no-1oad conditions, since only a slight movement of the valve head 61 from the cylindrical seat 62 is necesisary before the holding force on the driven member 31 is reduced to substantially zero.

The form of coengaging clutch teeth illustrated in Figs. 4 and 5, constituting a portion of the primary clutch 1S, is such that the clutch automatically compensates for the effects of inertia forces, depending upon the extent of resistance encountered by the threaded fastening element when it is being rotated by the apparatus. As disclosed in Figs. 4 and 5, the driving clutch teeth 27 have their end portions 109 substantially semi-circular in, section, and these crutch teeth engage generally concave tooth faces 29 on the driven clutch teeth 30. When the driven clutch member 31 is fully engaged with the driving clutch member 21, the clutch teeth occupy the position illustrated in Fig. 4, in which a tangent T, at the point of contact R between the driving and driven clutch teeth makes a relatively large angle P to a line through the point of contact and parallel to the axis of the device. The holdingforce of the air under pressure acting upon the valve head 61 may be indicated by :he vector F1, and this holding force is being exerted in a direction parallel to the axis of the apparatus. The resultant force F3 is being transmitted along a line normal to the tangent T1 at the point of contact. From the vector diagram, it is evident that a torque corresponding to a holding force F2 must be transmitted before the holding force F1 is overcome and the clutch released.

In the event that partial separation between the driving and driven clutch members is allowedto take place, then the teeth will engage at the point S, such as represented in Fig. 5, the engagement taking place along a steeper portion of the concave curve 29 on the driven tooth 30, or at a tangent line T2 drawn through the point of contact. The holding force F1 exerted by the same air pressure on the valve head 61 and tending to maintain the clutch teeth 27, 30 coengaged is the sameas in Fig. 4. However, due to the steeper slope of the tangent T2 to the point of contact S, the resultant force F5 being transmitted along the line normal to this tangent line is much greater, which indicates that a much greater force F4, corresponding to the torque being transmitted between the teeth, must be present before the holding force F1 will be overcome. ln other words, the torque transmitted prior to primary clutch release must be much greater under the conditions depicted in Fig, 5, than under the conditions shown in Fig. 4, in which the tangent T1 at the point of contact makes a much larger angle P to a line parallel to the axis of the equipment.

The clutch tooth forms disclosed in Figs. 4 and 5 are availed of to compensate for the effect of inertia forces, tending to tighten the threaded fastening element to a greater extent than actually corresponds to the holding force F1 exerted by the air under pressure 4acting upon the valve head 61. The holding force acts through the relatively high rate or stift" spring S6, to tend to maintain the driven clutch teeth 30 in engagement with the driving clutch'teeth 27. In the form of invention shown in Figs. 1, 2 and 3, this spring is necessary to allow the driven clutch teeth 30 to move partially toward a disengaged position with respect to the driving clutch teeth 27, without removing the valve head 61 from engagement with its companion cylindrical seat 62. The spring 56, however, is comparatively stiif and is incapable of collapsing or yielding sufficiently to permit the driven clutch teeth 30 to come out of engagement from the driving clutch teeth 27, when the valve head 61 is in engagement with its companion valve seat 62.

Under no-load conditions, the clutch teeth 27, 30 are fully engaged, as illustrated in Fig. 4, in which a comparatively low torque, represented by the vector F2, need be transmitted before the driven clutch member 31 is shifted axially out of engagement from the driving clutch member 21, when the holding force on the valve head 61 isovercome. lf a fast opening torque is imposed on the equipment, which corresponds to the rotation of a free running threaded fastener that comes to a sudden stop, then the sudden imposition of the torque, corresponding to the force F2, on the clutch teeth acts through the helical spring 56 to shift the valveA stem 51 and the valve head 61 out of engagement from the seat 62, releasing the holding force on the primary clutch 18 and enabling it to be shifted very rapidly and under no-load conditions to a fully released position, as illustrated in Fig. 3, Due to the sudden stopping of the threaded fas* tening element, it will be tightened beyond the value corresponding to the torque required to release the clutch 18,

inasmuch as inertia forces are brought into play that add to its tightening. That is, the total torque to which the threaded fastening element has been tightened is the sum of the static torque F2 corresponding to the holding force of the air under pressure against the valve head 61 plus a dynamic torque corresponding to the inertia of the parts and the impact to which the threaded fastening element is subjected when it comes to the sudden stop.`

If, however, the threaded fastening element does not come to a sudden stop, but `encounters comparatively gradual torque resistance during its tightening, the driven member 31 will be shifted by the torque transmitted axially away from the driving member 21, the valve head 61 remaining, at rst, fully engaged with its seat 62, because of the fact that the spring 56 intervening between the plate 47 and the valve stem 51 can yield. However, due to the partial axial shifting of the driven clutch teeth 30 with respect to the driving clutch teeth 27, the point of engagement S between the driving and driven clutch teeth shifts to a higher location on the teeth, at which the tangent Tz to the point of Contact is steeper. Accordingly, as illustrated in Fig. 5, despite the fact that the same holding force F2 is acting on the valve head. 61, tending to maintain the clutch teeth 27, 30 in engagement, the torque F4, corresponding to this holding force, and at which the holding force is overcome to release the clutch, is much greater. Accordingly, when the threaded fastening element encountering gradually increasing resistance is rotated, the primary clutch 18 actually fully releases at' a higher torque value than Was the case depicted in Fig. 4, in which a sudden imposition of the maximum torque was imposed upon the threaded fastening element. The static torque F4 of the threaded fastening element being gradually tightened is much greater than the static torque F2 when the threaded fastening element was stopped suddenly. The dynamic torquedue to the inertia forces is corre spondingly lower, inasmuch as the threaded fastening element and the .driven clutch member 31 have been more gradually decelerated. The sum of the torques, namely the static torque, which is greater, and the dynamic torque, which is less, will still substantially equal the desired final torque to be imposed upon the threaded fastening element. p

It is evident that, depending upon the degree of deceleration of the threaded fastening element against the work, the point of engagement of the driving and driven clutch teeth at the time that clutch release occurs will vary. The greater the dynamic torque due to inertia forces, the lesser will be the slope of the tangent at the point of contact, and the lesser will be the static torque. Conversely, the greater the static torque, due to the gradual imposition of the torque on the threaded fastening element and on the primary clutch parts, the lesser will be the dynamic torque, in view of the fact that the slope of the tangent T2 increases as the clutch teeth separate. i

It is, of course, possible to shape the concave faces 29 of the driven clutch teeth 30, so that the total torque to which a threaded fastening element is tightened when the threaded fastening element gradually comes to rest may be made greater than the torque to which the threaded fastening element is tightened upon a sudden stop. Then again, the converse may be true, or the torques `may be made equal, depending upon the particular shape of the concave faces of the driven teeth.

Accordingly, the tooth shape illustrated in Figs. 4 and 5 can produce essentially the same torque to which the threaded fastening element is tightened, regardless of the fact that the clutch may open rapidly, as when the threaded fastening element comes to a sudden stop, or when the clutch is opened slowly, when the threaded fastening element comes to a gradual stop.

With the tooth forms shown in Figs. 4 and 5, the intervening high rate or relatively stiff spring 56 between t the plate 47 and the valve stem 51 is provided to allow for the partial separation between the driving and driven clutch teeth27, 30 without shifting the valve head 61 from its seat 62. As noted above, the travel of the valve head to disengage it from its seat, and reduce the holding force on the driven clutch member to zero, is very 'i 1 little, being of the order, for example, of only a sixteenth of an inch. The driven clutch member 31, however, may shift partially to a greater axial extent than a sixteenth of an inch in shifting the point of contact R, S between the driving and driven clutch teeth, at which the holding force on the valve head is to be overcome. The intervening spring 56 enables sucient shifting to take place, to hold the clutch teeth 27, 30 engaged, while still avoiding disengagement of the valve head 61 from its companion seat 62.

In the form of invention illustrated in Figs. 6 and 7, the intervening spring 56 between the plate 47 and the retainer snap ring 57 on the stem 51 has been eliminated, and the hub 52 of the plate engages the snap ring S7 di rectly, so that the plate 47 cannot move axially with respect to the stem 51. With this form of the invention, and with the shape of the clutch teeth 27, 30 illustrated in Figs. 4 and 5 on the driving and driven members, partial axial separation between the driving and driven members can occur without shifting the valve head 61 from its seat 62. This is due to the fact that the cylindrical seat 62, engaged by the valve head, is made substantially longer than the seat shown in Figs. 1, 2 and 3. Accordingly, shifting of the driven member 31 to a partial extent toward a disengaged position `can occur, the seal ring 73 on the valve head still remaining in sealing engagement with the cylindrical seat 62 (see Fig. 7). The extent of shifting is sucient to cover the desired range of operation of the primary clutch 18 in effectively tight- 1 In the form of invention shown in Fig. 8, magnetic means is employed for holding the clutch teeth 27, 30 engaged, rather than the iluid means in the forms illustrated in Figs. l to 7, inclusive. Thus, the stop member 64, within the driving clutch member 21 functions as a holder for a permanent magnet 110 disposed wtihin its cavity or sprocket 111. A suitable brass bushing 112 intervenes between the periphery of the magnet and the wall of the socket, the magnet engaging a pole piece 113, which is contactable by an armature 114 mounted on the stem l which extends through the plate 47 secured to the driven member 31 of the primary clutch. As illustrated in Fig. 8, this plate 47 can slide in a clutch releasing direction along the armature stem 51 against the resistance of the relatively high rate or stiff spring 56, one end of which bears against the hub 52 of the plate, and the other end against the snap ring 57 secured to the stem 51.

The shape of the clutch teeth 27, 30 shown in the magnetic version of the apparatus may be the same as illustrated in Figs. 4 and 5. In the event that the primary cluteh i8 is operating under light loads, the clutch teeth will occupy the position disclosed in Fig. 4, the threaded fastening element coming to a sudden stop and the armature 114 being pulled away from the magnet 110, 113 in order to reduce the holding force of the magnet on the armature to substantially zero, and allowing full disengagement of the driven member clutch teeth 30 from the driving member teeth 27 to take place.

In the event of the load increasing gradually, then the driven member 31 is shifted away from the driving member 21, such shifting being permitted without removing the armature 114 from engagement with the pole piece 113 of the magnet 11i), because of the ability of the high rate compression spring 56 to yield. Such yielding reduces any inertia forces that might be effective on the threaded fastening element, and it also shifts the point of contact between the driving and driven clutch teeth to a position S in which the slope of the tangent T2 is increased, which might be, for example, to the position illustrated in Fig. 5. As explainedabove, under this condition, a greater torque is necessary to overcome the holding force of the magnet 110, and when the torque transmitted overcomes such holding force, the armature 114 is moved away from the pole piece 113 and the driven member 31 then rapidly shifted under 11o-load conditions to a fully released position, corresponding to the position shown in Fig. 3 of the fluid operated embodiment of the invention.

Thus, it is apparent that when the clutch 18 is running under a light load the point R of torque release is at a low tangent angle on the concave curve 29, the static torque necessary to release the clutch being comparatively low; Whereas, under such light load conditions the torque corresponding to the inertia forces is comparatively high. If the load on the clutch increases gradually, then the clutch teeth 27, 30 move relative to each other so that the point of contact S between them progresses along the concave faces of the teeth, the tangent T2 at the point of contact beco-ming steeper and requiring a greatertorque to release. However, the ability of the clutch members 21, 31 to move angularly with respect to one another minimizes the inertia forces imposed on the driven clutch member 31 and on the threaded fastening element, decreasing the torque attributable to the inertia forces, the static torque, however, being increased with respect to the example previously mentioned.

The spring 56 intervening between the plate 47 and the armature stem 51 enables the driven clutch teeth. 30 to move partially from engagement with the driving clutch teeth 27, while still maintaining the armature 114 engaged with the pole piece 113.

As previously described, the clutch teeth 30 on one of the members are concave, as disclosed in Figs. 4 and 5, in order to accomplish the aforementioned desirable results. Such shapes of teeth may be used with an intervening spring 56 between the member 61 or 114 on which the holding force is exerted and one of the clutch members, such as the driven member 31; or in the absence of such a spring with the apparatus disclosed in Figs. 6 and 7. When the intervening high rate spring 56 is used, a different form of clutch tooth can be employed to accomplish the objectives of the invention.

As shown in Figs. 1l and l2, straight sided driving and driven teeth 27a, 30a may be employed on the driving and driven clutch members 21, 31, these teeth having-coengaging inclined cam faces 27h, 29a, so that the torque transmitted therebetween tends to shift one of the clutch members, such as `the driven clutch member 31, toward a released position. When the primary clutch 18 is running under 11o-load, as when the threaded fastening element is free running, the teeth are fully engaged, as illustrated in Fig. ll, and the holding force of the high rate spring 56 is low. If a load is suddenly imposed upon the clutch members 21, 31, as caused by a sudden stop of the threaded fastening element upon the work, the driven member 31 tends to rnove away from the driving member 21, but such movement takes place against the force of the spring S6 intervening between the plate 47 and the stem 51. Because of the use of the high rate or stiff spring 56, this force is at rst small, but increases quickly upon slight spring compression to a large value. By the time the spring force has increased to the greatly larger value, which force is preferably still less than the holding force maintaining the valve head 61 within its seat 62, or the armature 114 engaged with the magnet 110, the effort to suddenly decelerate the moving clutch parts and axially accelerate the driven clutch member has been expended, the spring 56, in effect, acting as a yieldable device for cushioning the member 31. Accordingly, the inertia forces tending to tighten the fastening element to a greater extent have been offset or minimized to a considerable extent.

When the clutch members 21, 31 have been moved i assees apart by the load being transmitted to the extent at which the force exerted by the compressed spring 56 equals or exceeds the constant holding force of the air pressure on the valve head 61, or of tire magnet 110 on the armature 114, the head or armature is released from its holding position, so that the clutch teeth are then shifted rapidly to fully disengaged position under comparatively no-load conditions.

In the event the primary clutch is fully engaged under a no-load condition and the load gradually increases,

as due to the threaded fastening element gradually en countering resistance, the driven clutch teeth 30a tend to niove away from the driving clutch teeth 27a, the point of contact between the teeth moving up the teeth until a position is reached where the force of the spring 56 has increased sutliciently to stop further relative movement. As an example, the threaded fastening element may encounter a burr or rough spot on the thread, which will impart some torque resistance on the apparatus, but not the final torque desired at which the primary clutch is fully disengaged. When the threaded fastening element moves past such point of resistance, then the clutch is again running under a relatively low load, the spring 6 reshifting the driven clutch teeth 30a back into full engagement with the driving clutch teeth 27a. In this manner, the spring 56 continues to adjust the balance between the torque output and the force exerted by the spring 56. Under the condition mentioned, if the burr had been encountered without the spring being present, then the sudden deceleration of the clutch parts would have imposed inertia forces on the mechanism to the extent that the holding force of the valve head 61 or armature 114 may have been completely overcome and the clutch released prematurely.

If the load increases gradually on the threaded fasten ing element and on the clutch 18, the point of contact moves up the faces of the straight teeth 27h, 29a until the spring load of the compressed spring 56 equals or exceeds the constant holding force of the magnet 114 on the armature or of `the air pressure on the valve head 61, these latter elements then being released, allowing the clutch to shift rapidly to fully disengaged position under no-load conditions.

It is, accordingly, apparent that with the use of the straight cam tooth faces 27b, 29a illustrated in Figs. 11 and 12, and the intervening cushioning spring 56 of high rate, yieldability is incorporated in the mechanism at which the inertia forces are prevented from being imposed upon the clutch 18, so as to cause its disengagement at too low a value. Such inertia forces are also prevented from being imposed upon the threaded fastening element itself, since the driving clutch member 21 can move angularly relative to the driven clutch member 31, as a result of the slope of the cam teeth 27a, 30a, without disengaging the clutch, the driven member 31 moving axially away, to a partial extent at least, from the driving clutch teeth 27a. Accordingly, the effect of inertia forces tending to subject the threaded fastening element to greater torque, if the threaded fastening element comes to a sudden stop, is reduced, the apparatus being capable of torquing fastening elements that are gradually tightened to the same total torque as threaded fastening elements that are suddenly tightened.

The inventors claim:

1. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to disengage said teeth from each other; holding means exerting a holding force on said teeth tending to maintain them in engagement with each other; and yieldable means between said holding means and one of said members through which the holding force exerted by fr r..

other while said holding means continues to exert a holding force on said teeth; said yieldable means being incapable of yielding sufficiently to permit disengagement between said teeth before the 1nolding force of said holding means is overcome by the torque being transmitted between said teeth.

2, In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to disengage said teeth from each other; holding means exerting a holding force on said teeth tending to maintain them in engagement with each other; and a high rate spring between said holding means and one of said members through which the holding force exerted by said holding means is transmitted, said spring enabling said driving and driven clutch teeth to shift partially in a disengaged direction with respect to each other while said holding means continues to exert said holding force on said teeth; said spring being suciently stiff to prevent disengagement between said teeth before the` holding force of said holding means is overcome by the torque being transmitted between said teeth.

3. t In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the teeth of the other of said members; each tooth von said other member making substantially point contact with a companion concave face of a tooth on said one member, which point of contact shifts as said driving and driven clutch teeth separate, a tangent to said point of contact making a progressively lesser angle to a line through the point of contact and parallel to the axis of said members as said driving and driven clutch teeth separate; and holding means exerting a constant force on said teeth tending to maintain them in engagement with each other.

4. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the teeth of the other of said members; each tooth on said other member making substantially point contact with a companion concave face of a tooth on said one member, which point of contact shifts as said driving and driven clutch teeth separate, a tangent to said point of contact making a progressively lesser angle to a line through the point of contact and parallel to the axis of said members as said driving and driven clutch teeth separate; holding means exerting a constant force on said teeth tending to maintain them in engagement with each other; and yieldablemeans between said holding means and one of said members enabling said driving and driven clutch teeth to shift partially in a disengaged direction with respect to each other to change the points of contact between said concave faces and the teeth of the other of said members while said holding means continues to exert a holding force on said teeth.

5. In torque transmitting apparatus; driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having straight tapered faces engaged by the teeth of the other of said members; holding means exerting a holding force on said teeth tending to maintain them in engagement with each other;

and yieldable means between said holding means and one of said members through which the holding force exerted by said holding means is transmitted, said yieldable means enabling said driving and driven clutch teeth to shift partially in a disengaging direction with respect to each other while said holding means continues to exert a holding force on said teeth.

6. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the teeth of t-he other of said members; each tooth on said other member making substantially point contact with a companion concave face of a tooth on said one member, which point of contact shifts as said driving and driven clutch teeth separate, a tangent to said point of contact making a progressively lesser angle to a line through the point of contact and parallel to the axis of said members as said driving and driven clutch teeth separate; holding means exerting a constant force on said teeth tending to maintain them in engagement with each other; and means including a high rate spring between said holding means and one of said members enabling said driving and driven clutch teeth to shift partially in a disengaged direction with respect to each other to change the point of contact between said concave faces and the teeth of the other of said members while said holding means continues to exert a holding force on said teeth.

7. ln torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between .said members; the clutch teeth on some of said members having straight tapered faces engaged by the teeth of the other of said members; holding means exerting a holding force on said teeth tending to maintain them in engagement with each other;.and a high rate spring between said holding means and one of said members through which the holding force exerted by said holding means is transmitted, said spring enabling said driving and driven clutch teeth to shift partially in a disengaging direction with respect to each other while said holding means continues to exert a holding force on said teeth.

8. in torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the teeth of the other of said members; each tooth on said other meniber making substantially point contact with a companion concave face of a tooth on said one member, which point of contact shifts as said driving and driven clutch teeth separate, a tangent to said point of contact making a progressively lesser angle to a line through the point of Contact and parallel to the axis of said members as said driving and driven clutch teeth separate; and means responsive to fluid under pressure differential for exerting a holding force on said teeth tending to maintain them in engagement with each other.

9. ln torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the teeth of the other of said members; each tooth on said other member making substantially point Contact with a companion concave face of a tooth on said one member, which point of contact shifts as said driving and driven clutch teeth separate, a tangent to said point of contact making a progressively lesser angle to a line through the point of Contact and parallel to the axis of said members as said driving and driven clutch teeth separate; means responsive to' fluid under pressure differential for exerting a holding force on said teeth tending to maintain them in engagement with each other; said means including a valve body having a cylindrical seat, and a valve head engageable in said seat and movable in a direction out of engagement from said seat as the torque transmitted between said driving and driven clutch teeth increases, said valve head being fully engaged in said seat when said driving and driven clutch teeth are fully engaged, said valve head remaining engaged in said seat upon partial disengagement between said driving anddriven clutch teeth.

l0. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the' teeth of the other of said members; magnetic means exerting a holding force on said teeth tending to maintain them in engagement with each other; and yieldable means between said magnetic means and one of said members through which the holding force exerted by said magnetic means is transmitted, said yieldable means enabling said driving and driven clutch teeth to shift partially in a disengaging 'direction with respect to each other to change the point of contact between said concave faces and the teeth of the other of said members while said magnetic means continues to exert a holding force on said teeth.

l1. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having straight tapered faces engaged by the teeth of the other of said members; means responsive to fluid under pressure differential for exerting a holding force on said teeth tending to maintain them in engagement with each other; and yieldable means between said uid responsive means and one of said members through which the holding force exerted by said fluid pressure responsive means is transmitted, said yieldable means enabling said driving and driven clutch teeth to shift partially in a disengaging direction with respect to each other while said means responsive to fluid pressure continues to exert a holding force on said teeth.

l2. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having straight tapered faces engaged by the teeth of the other of said members; magnetic means exerting a holding force on said teeth tending to maintain them in engagement with each other; and yieldable means between said magnetic means and one of said members through which the holding force exerted by said magnetic means is transmitted, said yieldable means enabling said driving and driven clutch teeth to shift partially in a disengaging direction with respect to each other while said magnetic means continues to exert a holding force on said teem.

13. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to disengage said teeth from each other; holding means exerting a holding force on said teeth tending to maintain them in engagement with each other, said holding means comprising first instrumentalities rotatable with said driving member, second instrumentalities rotatable with said driven member and engageable with said first instrumentalities, and yieldable means between one of said instrumentalities and one of said members through which the holding force exerted by said holding means is transmitted, said yieldable means enabling said driving and driven clutch teeth to shift partially in adisengaged direction with respect to each other while said first and second instrumentalities remain coengaged to continue to exert a holding force on said teeth.

\ `assassin 14. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to shift said driven member axially and disengage said teeth from each other; holding means acting between said driving and driven members and tending to exert a holding force on said driven member to prevent axial movement of said driven member and disengagement between said driving and driven clutch teeth, said holding means including a yieldable connection through which the holding force exerted by said holding means is transmitted, said yieldable connection permitting partial axial shifting of said driven member while said holding means continues to exert a holding force on said teeth; said yieldable connection being incapable of yielding suiiciently to permit disengagement between said teeth before the holding force of said holding means is overcome by the torque being transmitted between said teeth.`

l5.' In torque transmitting apparatus: driving and driven members, coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to disengage said teeth from each other; axially movable holding means engageable with one of said members to hold said clutch teeth in driving relation to each other, said teeth tending to shift said holding means axially to release said teeth from such driving relation; means for exerting an axially directed force on said holding means in opposition to the force exerted on said holding means by said teeth while torque is being transmitted through said teeth, said exerting means releasing its force on said holding means upon initial minute axial movement of said holding means from engagement with said one of said members; said holding means embodying a yieldable connection through which the holding force exerted by said holding means is transmitted, said yieldable means permitting partial disengagement between said teeth without disengaging said holding means from said one of said members; said yieldable connection being incapable of yielding suliciently to permit disengagement between said teeth before the holding force of said holding means is overcome by the torque being transmitted between said teeth.

i6, in torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to shift said driven member axially and disengage said teeth from each other; axially movable holding means connected to said driven member and engageable with said driving member to hold said clutch teeth in driving relation to each other, said teeth tending to shift said holding means axially to release said teeth from such driving relation; means for exerting an axially directed force on said holding means in opposition to the force exerted on said holding means by said teeth while torque is being transmitted through said teeth, said exerting means releasing its force on said holding means upon initial minute axial movement of said holding means from engagement with said driving member; said holding means embodying a yieldable connection through which the holding force exertedby said holding means is transmitted, said yieldable connection permitting partial axial movement of said driven member with respect to said driving member and partial disengagement between said teeth without disengaging said holidng means from said driving member; said yieldable connection being incapable of yielding suiciently to permit disengagement 18 A between said teeth before the holding force of said holding means is overcome by the torque being transmitted between said teeth.

17. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members eiiecting a rotatable driving iconnection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to disengage said teeth from each other; holding means exerting a holding force on said teeth tending to maintain them in engagement with each other, said holding means comprising first instrumentalities rotatable with said driving member, second instrumentalities rotatable with said driven member and engageable with said iirst instrumentalities, and a high rate spring between one of said instrumentalities and one of said members through which the holding force exerted by said holding means is transmitted, said spring enabling said driving and driven clutch teeth to shift partially in a disengaged direction with 4respect to each other while said second instrumentalities remain coengaged to continue to exert a holding force on said teeth; said spring being suhciently stiff to prevent disengagement between said teeth before the holding force of said holding means is overcome by the torque being transmitted between said teeth.

18. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one 0f said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to shift said driven member axially `and disengage said teeth from each other; holding means acting between said driving and driven members and tending to exert a holding force on said driven member to prevent axial movement of said driven member and disengagement between said driving and driven clutch teeth, said holding means including a high rate spring connection with said driven member through which the holding force exerted by said holding means is transmitted, said spring connection permitting partial axial shifting of said driven member while said holding means continues to exert a holding force on said teeth; said spring being suiiiciently stii to prevent disengagement between said. teeth before the holding torce of said holding means is overcome by the torque being transmitted between said teeth.

19, In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to disengage said teeth from each other; axially movable holding means engageable with one of said members to hold said clutch teeth in driving relation to each other, said teeth tendingy to shift said holding means axially to release said teeth from such driving relation; means for exerting an axially directed force on said holding means in opposition to the force exerted on said holding means by said teeth while torque is being transmitted through said teeth, said exerting means releasing its force on said holding means upon initial minute axial movement of said holding means from engagement with said one of said members; said holding means embodying a high rate spring through which the holding force exerted by said holding means is transmitted, said spring permitting partial disengagement between said teeth without disengaging said holding means from said one of said members; said spring being sufficiently stiii to prevent disengagement between said teeth before the holding -torce of said holding means is overcome by the torque being transmitted between said teeth.

20. In torque transmitting apparatus: driving and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members, the teeth on at least one of said members being tapered, in order that the torque transmitted between said driving and driven teeth tends to shift said driven member axially and disengage said teeth from each other; axially movable holding means connected to said driven member and engageable with said driving member to hold said clutch teeth in driving relation to each other, said teeth tending to shift said holding means axially to release said teeth from such driving relation; means for exerting an axially directed force on said holding means in opposition to the force exerted on said holding means by said teeth WhileV torque is being transmitted through said teeth, said exerting means releasing its force on said holding means upon initial minute laxial movement of said holding means from engagement with said driving member; said holding means embodying a high rate spring connection with said driven member through which the holding force exerted by said holding means is transmitted, said spring connection permitting partial axial movement of said driven member with respect to said driving member and partial disengagement between said teeth without disengaging said holding means from said driving member; said spring being sufficiently stii to prevent disengagement between said teeth before the holding force of said holding means 20 is overcome by the torque being transmitted between said teeth.

21. in torque transmitting apparatus: driving 'and driven members; coengaging driving and driven clutch teeth on said members effecting a rotatable driving connection between said members; the clutch teeth on one of said members having concave faces engaged by the teeth of the other of said members; each tooth on said other member making substantially point contact with a companion concave face of a tooth on said one member, which point of contact shifts as said driving and driven clutch teeth separate, 'a tangent to said point of contact making a progressively lesser angle to a line through the point of Contact and parallel to the axis of said members as said driving and driven clutch teeth separate; and holding means exerting a force on said teeth tending to maintain them in engagement with each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,068,260 Biggert Jan. 19, 1937 2,299,956 Stever Oct. 27, 1942 2,464,590 Landahl Mar. 15, 1949 2,683,512 Boice July 13, 1954 

